The present invention relates to a method for manufacturing a sintered body, in which the sintered body is formed by sintering an extruded body comprised of metal powder.
Hot extrusion for extruding a metal material through an extrusion die and for forming the metal material into a predetermined shape has been well known. By the extrusion mentioned above, for example, a metal product in a continuous form can be manufactured.
However, in the hot extrusion described above, the production facility is large, and the metals which can be used are limited (for example, high speed steel, die steel, hard material, and the like, are difficult to be processed by hot extrusion), and in addition, there is a problem in that dimensional accuracy of the metal product is poor.
An object of the present invention is to provide a method for manufacturing a sintered body, in which there is a large degree of freedom for selecting usable metals and a metal product (particularly, a product in a continuous form or a product cut therefrom) having superior dimensional accuracy can be easily obtained.
The object described above can be achieved by the present invention described in (1) to (8) below.
(1) A method for manufacturing a sintered body comprises an extruding molding step of extruding a feed stock comprising metal powder and a binder from an extrusion die of an extruder so as to form an extruded body,
a debinding step of debinding the extruded body, and
a sintering step of sintering the debound extruded body so as to manufacture the sintered body,
wherein, in the extrusion molding step, the extrusion die is provided with a temperature gradient along the extrusion direction.
(2) The temperature gradient described above is preferably provided so that a temperature of the extrusion die at an extrusion opening side is lower.
(3) The feed stock described above preferably further comprises an organic material having a melting point which is lower than that of the binder.
(4) The organic material preferably functions as a binder.
(5) The melting point of the binder is preferably 80 to 300xc2x0 C. and the melting point of the organic material is preferably xe2x88x9250 to 80xc2x0 C.
(6) The extrusion molding step described above is preferably performed at a temperature of the extrusion die of less than the melting point of the binder and more than the melting point of the organic material in the vicinity of the extrusion opening.
(7) The extrusion molding described above is preferably performed in which a temperature of the extrusion die in the vicinity of the extrusion opening is controlled using a cooling unit and a heating unit.
(8) The debinding step preferably further comprises a first process of debinding performed in a low temperature region and a second process of debinding performed in a temperature region higher than that in the first process.